Molecular characterization of rotaviruses obtained from patients with rotavirus-associated encephalitis/encephalopathy.

Group A rotavirus (RVA) rarely causes severe complications such as encephalitis/encephalopathy. However, the pathophysiology of this specific complication remains unclear. Next-generation sequence analysis was used to compare the entire genome sequences of RVAs detected in patients with encephalitis/encephalopathy and gastroenteritis. This study enrolled eight patients with RVA encephalitis/encephalopathy and 10 with RVA gastroenteritis who were treated between February 2013 and July 2014. Viral RNAs were extracted from patients' stool, and whole-genome sequencing analysis was carried out to identify the specific gene mutations in RVA obtained from patients with severe neurological complications. Among the eight encephalitis/encephalopathy cases, six strains were DS-1-like G1P[8] and the remaining two were Wa-like G1P[8] (G1-P[8]-I1-R1-C1-M1-A1-N1-T1-E1-H1). Meanwhile, eight of the 10 viruses detected in rotavirus gastroenteritis patients were DS-1-like G1P[8], and the remaining two were Wa-like G1P[8]. These strains were further characterized by conducting phylogenetic analysis. No specific clustering was demonstrated in RVAs detected from encephalitis/encephalopathy patients. Although the DS-1-like G1P[8] strain was predominant in both groups, no specific molecular characteristics were detected in RVAs from patients with severe central nervous system complications.

Persistent systemic rotavirus vaccine infection in a child with X-linked severe combined immunodeficiency.

OBJECTIVE: The main aims of the present study were to elucidate the systemic group A rotavirus (RVA) infection and to clarify the genetic changes of persistent virus in the X-linked severe combined immunodeficiency (SCID) patient. METHODS: RotaTeq vaccine (RV5) genotype-specific real-time reverse transcription polymerase chain reaction was used to monitor viral RNA load in serially collected serum and stool samples. Next-generation sequence analysis was used to determine the genotype of the virus by sequencing 11 gene segments. Polyacrylamide gel electrophoresis (PAGE) analysis was used to identify rearrangement of viral genes. The gene rearrangement was examined in NSP5 gene by using Sanger sequence. RESULTS: A 7-month-old boy demonstrated chronic diarrhea following the third administration of RV5 and failure to thrive. He was diagnosed with X-linked SCID and successfully underwent cord blood transplantation. High copy numbers of RV5 genotype G1 RNA were detected in serially collected stool and serum samples and the kinetics of viral RNA loads were correlated with the degree of clinical disease. Next-generation sequence analysis revealed genetic reassortment at least between the strains WI79-9/G1P7[5] and WI79-4/G6P1A[8] in the VP7 gene and the VP4 gene among the vaccine-derived rotavirus strains. In addition, PAGE analysis suggested genetic rearrangements in several genes, and it was confirmed in the NSP5 gene by sequence analysis. CONCLUSIONS: The kinetics of RVA RNA load in serum and stool samples was consistent with the clinical course of the patient. Among five genotypes of RV5 vaccine, G1 genotype replicated well in this patient. Reassortment and rearrangements were demonstrated in persistently infected G1 genotype of RV5.

Rotavirus Vaccination Can Be Performed Without Viral Dissemination in the Neonatal Intensive Care Unit.

Background: This study was conducted to assess the transmissibility of rotavirus vaccine strains after rotavirus vaccination in a neonatal intensive care unit (NICU). Methods: Pentavalent (RV5) or monovalent (RV1) rotavirus vaccine was administered to infants admitted to the NICU. Nineteen vaccinated infants and 49 unvaccinated infants whose beds were located in close proximity to the vaccinated infants were enrolled in this study. Dissemination and fecal shedding of vaccine viruses within the NICU were examined using real-time reverse transcription-polymerase chain reaction. Results: Shedding of the vaccine strain was detected in all 19 vaccinated infants. RV5 virus shedding started 1 day after the first vaccination and persisted for 8 days after the first vaccination, and viral shedding terminated by day 5 after administration of the second RV5 dose. The kinetics of RV1 virus shedding differed among vaccinated infants. The duration of RV1 virus shedding was longer after the first vaccination than after the second vaccination. In contrast to the vaccinated infants, no vaccine virus genomes were detected in any of the stool samples collected from the 49 unvaccinated infants. Conclusions: This study is direct evidence of no transmission of rotavirus vaccine strains between vaccinated infants and unvaccinated infants in close proximity within a NICU.

Development of real-time RT-PCR assays for detection of three classes of HHV-6A gene transcripts.

Human herpesvirus 6 (HHV-6), a member of the betaherpesvirus family, has two distinct species: HHV-6A and HHV-6B. HHV-6B real-time reverse transcription polymerase chain reaction (RT-PCR) has been used to distinguish between active and latent viral infection. In this study, we developed a real-time RT-PCR assay to detect HHV-6A-specific transcripts and evaluated its reliability for analysis of clinical samples. To develop HHV-6A-specific real-time RT-PCR assays, three different classes of gene transcripts (immediate early: U90; early: U12; and late: U100) were selected as targets. Serial d ilutions of plasmid DNAs containing target sequences and RNAs extracted from HHV-6A-infected cells were used to determine assay specificity and sensitivity. Peripheral blood mononuclear cells (PBMCs) collected from patients with either primary or reactivated HHV-6B infection, and one patient with X-linked severe combined immunodeficiency (X-SCID) with HHV-6A reactivation, were used to evaluate assay reliability. The HHV-6A-specific real-time RT-PCR assays amplified plasmids containing the target sequences at concentrations between 10 and 1 × 106 copies per reaction. The intra-assay coefficients of variation were less than 5%. The three classes of HHV-6A gene transcripts were not detected in any HHV-6B sample isolated from the patients. In the X-SCID patient, high copy numbers of HHV-6A U12 and U100 transcripts were detected in PBMC samples during viremia. Thus, we successfully established highly sensitive and reproducible real-time RT-PCR methods targeting three classes of HHV-6A gene transcripts. This method should be useful for discriminating active HHV-6A infection from either latent infection or chromosomally integrated HHV-6A (ciHHV-6A).

Rotavirus vaccine strain transmission by vaccinated infants in the foster home.

Previous studies have demonstrated the transmission of rotavirus vaccine strains from vaccinated children to nonvaccinated siblings. We sought to fully elucidate the safety of rotavirus (RV) vaccination in closed contact circumstance, such as the foster home for future assessment of the vaccine safety in an neonatal intensive care unit. Stool samples were collected from 4 RV vaccinated (160 samples) and 23 unvaccinated (766 samples) infants. RV viral RNA loads were measured using real-time reverse transcription polymerase chain reaction (RT-PCR). RV vaccine strain RNA was persistently detected in stool samples collected from the four vaccine recipients and one unvaccinated infant, but not in the stool samples collected from the 22 other unvaccinated infants. The unvaccinated infant who tested positive for the RV vaccine strain was vaccinated prior to enrollment in this study. The quantitative real-time RT-PCR data revealed a peak viral RNA load 1 week after vaccination followed by a gradual decrease. The current study suggests that RV vaccination may be safe in a close contact environment because there was limited transmission from RV vaccinated to unvaccinated infants. J. Med. Virol. 89:79-84, 2017. © 2016 Wiley Periodicals, Inc.

Three infants with rotavirus gastroenteritis complicated by severe gastrointestinal bleeding.

Rotavirus gastroenteritis causes substantial morbidity and mortality worldwide in children. We report three infants with rotavirus gastroenteritis complicated by various severity of gastrointestinal bleeding. Two patients (cases 1 and 2) recovered completely without any specific treatments. One patient (case 3) died despite extensive treatments including a red blood cell transfusion and endoscopic hemostatic therapy. Rotavirus genotypes G1P[8] and G9P[8] were detected in cases 2 and 3, respectively. Rotavirus antigenemia levels were not high at the onset of melena, suggesting that systemic rotaviral infection does not play an important role in causing melena.

Molecular Epidemiology of Respiratory Syncytial Virus during 2019-2022 and Surviving Genotypes after the COVID-19 Pandemic in Japan.

To evaluate the changes in respiratory syncytial virus (RSV) collected between 2019 and 2022, we analyzed RSV-A and RSV-B strains from various prefectures in Japan before and after the COVID-19 pandemic. RT-PCR-positive samples collected from children with rapid test positivity at outpatient clinics in 11 prefectures in Japan were sequenced for the ectodomain of the G gene to determine the genotype. Time-aware phylogeographic analyses were performed using the second hypervariable region (HVR) of the G gene from 2012 to 2022. Of 967 samples, 739 (76.4%) were found to be RSV-positive using RT-PCR. RSV peaked in September 2019 but was not detected in 2020, except in Okinawa. Nationwide epidemics occurred with peaks in July 2021 and 2022. The genotype remained the same, ON1 for RSV-A and BA9 for RSV-B during 2019-2022. Phylogeographic analysis of HVR revealed that at least seven clusters of RSV-A had circulated previously but decreased to two clusters after the pandemic, whereas RSV-B had a single monophyletic cluster over the 10 years. Both RSV-A and RSV-B were transferred from Okinawa into other prefectures after the pandemic. The RSV epidemic was suppressed due to pandemic restrictions; however, pre-pandemic genotypes spread nationwide after the pandemic.

Development of a human herpesvirus 6 species-specific immunoblotting assay.

In order to assess the full spectrum of human herpesvirus 6A (HHV-6A)- and HHV-6B-associated diseases, we sought to develop an HHV-6 species-specific serological assay based on immunoblot analysis. The immunodominant proteins encoded by open reading frame U11, p100 for HHV-6A (strain U1102) and 101K for HHV-6B (strain Z29), were selected to generate virus species-specific antigens. Recombinant p100 and 101K were produced in a prokaryotic expression system. The expression of these proteins was confirmed by using anti-His tag and 101K-specific monoclonal antibodies. HHV-6 species-specific antibodies were detected by immunoblotting in patient sera. Eighty-seven serum samples obtained from various subjects were utilized to determine the reliability of the method for clinical use. Ten of twelve exanthem subitum convalescent-phase sera reacted exclusively with 101K, whereas none of twelve acute-phase sera reacted with either protein. Two of three sera collected from HHV-6A-infected patients reacted with p100 and 101K. Although all five acute and convalescent-phase sera obtained from transplant recipients reacted exclusively with 101K, two of six convalescent-phase sera obtained from patients with drug-induced hypersensitivity syndrome reacted with both p100 and 101K. Of 38 sera obtained from healthy adults, 31 were positive for 101K antibody, while 4 reacted with both proteins. However, PCR analysis of peripheral blood mononuclear cells and saliva from these subjects did not detect HHV-6A DNA. In conclusion, this novel serological assay based on immunoblot analysis using recombinant HHV-6A p100 and HHV-6B 101K allowed us to discriminate between HHV-6A- and HHV-6B-specific antibodies.

Correlation between serum matrix metalloproteinase and antigenemia levels in patients infected with rotavirus.

Rotavirus (RV) antigenemia has been reported in patients with gastroenteritis; however, the exact mechanism remains unclear. In order to elucidate the mechanism of RV antigenemia, an association between RV antigenemia and matrix metalloproteinase (MMP) were analyzed. The object of this study was to elucidate the role of MMPs and tissue inhibitors of metalloproteinases (TIMPs) in the pathogenesis of RV antigenemia. Forty children admitted to hospital with RV gastroenteritis were enrolled in this study. Paired serum samples were collected at the time of admission and discharge. Enzyme-linked immunosorbent assays (ELISA) were used to detect serum concentrations of viral antigens, MMP-1, -2, -9, -13, TIMP -1, and -2. Cytokines were measured using flow cytometric beads array. RV antigens were significantly higher in serum collected at the time of admission than discharge (P < 0.001). MMP-9 concentrations were significantly higher in serum collected at the time of admission than discharge (P < 0.001). MMP-2 concentrations were significantly lower in serum collected at the time of admission than discharge (P < 0.001). A weak but a significantly positive association (P = 0.034) was observed between RV antigen and MMP-9 in serum collected at the time of admission, and inverse association was observed between RV antigen and MMP-2. In addition, a weak but significantly positive association (P = 0.002) was observed between IL-6 and MMP-9. These data suggest that MMPs may contribute to the pathogenesis of RV antigenemia.

Development of quantitative RT-PCR assays for detection of three classes of HHV-6B gene transcripts.

The monitoring of active human herpesvirus 6 (HHV-6) B infection is important for distinguishing between the reactivation and latent state of the virus. The aim of this present study is to develop a quantitative reverse transcription polymerase chain reaction (RT-PCR) assay for diagnosis of active viral infection. Primers and probes for in house quantitative RT-PCR methods were designed to detect the three kinetic classes of HHV-6B mRNAs (U90, U12, U100). Stored PBMCs samples collected from 10 patients with exanthem subitum (primary HHV-6B infection) and 15 hematopoietic stem cell transplant recipients with HHV-6B reactivation were used to evaluate reliability for testing clinical samples. Excellent linearity was obtained with high correlation efficiency between the diluted RNA (1-100 ng/reaction) and C(t) value of each gene transcript. The U90 and U12 gene transcripts were detected in all of the peripheral blood mononuclear cells (PBMCs) samples collected in acute period of primary HHV-6B infection. Only one convalescent PBMCs sample was positive for the U90 gene transcript. Additionally, the reliability of HHV-6B quantitative RT-PCRs for diagnosis of viral reactivation in hematopoietic transplant recipients was evaluated. Relative to virus culture, U90 quantitative RT-PCR demonstrated the highest assay sensitivity, specificity, positive predictive value, and negative predictive value. Thus, this method could be a rapid and lower cost alternative to virus culture, which is difficult to perform generally, for identifying active HHV-6B infection.

Host factors associated with the kinetics of Epstein-Barr virus DNA load in patients with primary Epstein-Barr virus infection.

The aims of this study were to elucidate the kinetics of Epstein-Barr virus (EBV) DNA load in serially collected peripheral blood mononuclear cells of patients with primary EBV infection, and to determine the correlated host factors. Blood samples were collected from 24 patients with primary EBV infection. EBV DNA copy numbers were measured using real-time polymerase chain reaction. Based on the kinetics of EBV DNA load, the 24 patients were divided into two groups: rapid regression and slow regression. Eighteen of the 24 patients (75%) were included in the slow regression and 6 (25%) in the rapid regression group. No statistically significant differences were observed between the two groups in clinical features and laboratory findings. However, acute phase (3 to 10 days after the onset of the illness) serum samples from six children in the slow regression and four in the rapid regression group revealed significantly higher serum interleukin (IL)-1ß (P= 0.018), IL-12 (P= 0.009), tumor necrosis factor-α (P= 0.019), interferon-inducible protein 10, and monokine induced by interferon γ concentrations in the rapid regression than the slow regression group. On the other hand, sera from six children in the slow regression and four in the rapid regression group in the convalescent phase (14 to 21 days after the onset of the illness) showed no statistically significant differences between the two groups in these biomarker concentrations. Based on this, it was concluded that the kinetics of EBV DNA load can be divided to two different patterns after primary EBV infection, and immune response might be associated with viral clearance.

Cytokine and chemokine responses in pediatric patients with severe pneumonia associated with pandemic A/H1N1/2009 influenza virus.

Severe pneumonia and leukocytosis are characteristic, frequently observed, clinical findings in pediatric patients with pandemic A/H1N1/2009 influenza virus infection. The aim of this study was to elucidate the role of cytokines and chemokines in complicating pneumonia and leukocytosis in patients with pandemic A/H1N1/2009 influenza virus infection. Forty-seven patients with pandemic A/H1N1/2009 influenza virus infection were enrolled in this study. Expression of interleukin (IL)-10 (P = 0.027) and IL-5 (P = 0.014) was significantly greater in patients with pneumonia than in those without pneumonia. Additionally, serum concentrations of interferon-γ (P = 0.009), tumor necrosis factor-α (P = 0.01), IL-4 (P = 0.024), and IL-2 (P = 0.012) were significantly lower in pneumonia patients with neutrophilic leukocytosis than in those without neutrophilic leukocytosis. Of the five serum chemokine concentrations assessed, only IL-8 was significantly lower in pneumonia patients with neutrophilic leukocytosis than in those without leukocytosis (P = 0.001). These cytokines and chemokines may play important roles in the pathogenesis of childhood pneumonia associated with A/H1N1/2009 influenza virus infection.

Molecular Epidemiology of Norovirus (NoV) Infection in Mie Prefecture: The Kinetics of Norovirus Antigenemia in Pediatric Patients.

Few studies have shown the presence of norovirus (NoV) RNA in blood circulation but there is no data on norovirus antigenemia. We examined both antigenemia and RNAemia from the sera of children with NoV infections and studied whether norovirus antigenemia is correlated with the levels of norovirus-specific antibodies and clinical severity of gastroenteritis. Both stool and serum samples were collected from 63 children admitted to Mie National Hospital with acute NoV gastroenteritis. Norovirus antigen and RNA were detected in sera by ELISA and real-time RT-PCR, respectively. NoV antigenemia was found in 54.8% (34/62) and RNAemia in 14.3% (9/63) of sera samples. Antigenemia was more common in the younger age group (0-2 years) than in the older age groups, and most patients were male. There was no correlation between stool viral load and norovirus antigen (NoV-Ag) levels (rs = -0.063; Cl -0.3150 to 0.1967; p = 0.6251). Higher levels of acute norovirus-specific IgG serum antibodies resulted in a lower antigenemia OD value (n = 61; r = -0.4258; CI -0.62 to -0.19; p = 0.0006). Norovirus antigenemia occurred more commonly in children under 2 years of age with NoV-associated acute gastroenteritis. The occurrence of antigenemia was not correlated with stool viral load or disease severity.

Evaluation of reverse transcription loop-mediated isothermal amplification assays for rapid diagnosis of pandemic influenza A/H1N1 2009 virus.

Two genetic diagnosis systems using reverse transcription-loop-mediated isothermal amplification (RT-LAMP) technology were evaluated: one for detecting the HA gene of the pandemic influenza A/H1N1 2009 virus (H1pdm RT-LAMP) and the other for detecting the matrix gene of the influenza A virus (TypeA RT-LAMP). The competence of these two RT-LAMP assay kits for the diagnosis of the pandemic influenza A/H1N1 2009 virus was compared using real-time RT-PCR assays developed recently on viruses isolated and clinical specimens collected from patients with suspected infection. TypeA RT-LAMP and H1pdm RT-LAMP showed almost the same sensitivity as real-time RT-PCR for viruses isolated. The sensitivity and specificity of TypeA RT-LAMP and H1pdm RT-LAMP were 96.3% and 88.9%, respectively, for clinical specimens. Considering that the ability of the two RT-LAMP assay kits for detection of the pandemic influenza A/H1N1 2009 virus was comparable to that of the real-time RT-PCR assays, and that the assays were completed within 1 hr and did not require any expensive equipment, these two RT-LAMP assays are promising rapid diagnostic tests for the pandemic influenza A/H1N1 2009 virus at the hospital bedside.

A case of erythema multiforme associated with primary Epstein-Barr virus infection.

We present a case of primary Epstein-Barr virus (EBV) infection with erythema multiforme. A 1-year-old Japanese boy presented with skin eruptions, including typical target lesions and a low-grade fever. Just before the skin biopsy, 95 copies/µg DNA of EBV genome was detected in peripheral blood mononuclear cells, which subsequently increased to 6,834 copies/µg DNA. Skin tissue collected from the skin lesion showed the typical pathologic findings of erythema multiforme. EBV-encoded small nuclear RNA signals were not detected in the skin tissue by in situ hybridization.

Loop-mediated isothermal amplification for discriminating between human herpesvirus 6 A and B.

Genotyping of human herpesvirus 6 (HHV-6) is important clinically, particularly for the diagnosis of neurological diseases. The objective of this study was to establish a rapid HHV-6 genotyping method using the loop-mediated isothermal amplification (LAMP) method. An AccI site is located in the target sequence of HHV-6 B, but not in HHV-6 A. LAMP products were digested with the AccI enzyme and then separated by agarose gel electrophoresis to differentiate the digest pattern of the two variants. The fragment patterns were clearly different between HHV-6 A and B. In order to evaluate the reliability of this HHV-6 genotyping method for use in the clinical laboratory, serum samples from 20 patients with either primary HHV-6 infection or viral reactivation were collected and analyzed. HHV-6 DNA was amplified directly from the serum samples and all 20 LAMP products were positive for HHV-6 B.

Development of a new enzyme immunoassay for improved detection of rotavirus in fecal specimens of vaccinated infants.

BACKGROUND: Group A rotavirus is the most common cause of acute diarrhea in young children worldwide. A simple and rapid enzyme immunoassay (EIA) has been commonly used to detect rotavirus infection and evaluate rotavirus vaccines. Currently licensed commercial EIA kits have low sensitivity. A more sensitive detection of rotavirus can improve rotavirus diagnostics and vaccine efficacy studies. OBJECTIVE: A biotin-avidin based sandwich EIA was developed and compared with commercial EIA kits for improved detection of viral shedding in fecal samples from infants who received human rotavirus vaccine Rotarix in Mexico. STUDY DESIGN: A monoclonal antibody (mAb: 1D4) specific to human rotavirus group antigen VP6 was prepared and used to develop a biotin-avidin based sandwich EIA. This EIA was employed to test 128 fecal samples from vaccinated infants, in comparison with two commercial EIA kits using RT-PCR as a reference. RESULTS: A new biotin-avidin based sandwich EIA showed specific reaction to group A rotaviruses, but not to other enteric viruses. This new EIA had a detection rate of 36.7% for rotavirus antigen shedding in fecal specimens, which was two times higher (16.4%, 18.0%) than those from two commercial EIA kits. CONCLUSION: The new EIA had specificity and higher sensitivity than commercial kits. This new EIA has the potential to detect rotavirus at lower concentration in clinical specimens and thus should be further evaluated as a more sensitive kit for use in diagnostics and vaccine efficacy and effectiveness studies.

Direct detection of human herpesvirus 6 DNA in serum by the loop-mediated isothermal amplification method.

BACKGROUND: A more rapid and easier method is needed for monitoring human herpesvirus 6 (HHV-6) infections. The loop-mediated isothermal amplification method (LAMP) can detect viral DNA with high specificity, efficiency, and speed under isothermal conditions. LAMP requires only simple equipment that is available in hospital laboratories. OBJECTIVES: We evaluated LAMP as a means of detecting HHV-6 DNA directly from patients' sera. RESULTS: The sensitivity of the HHV-6 LAMP protocol without heat denaturation was 1000 copies/tube; with heat denaturation 10 copies/tube were detected. Three hundred serum samples from children with fever were analyzed. Using HHV-6 isolation as a definition of HHV-6 infection, the sensitivity, specificity, positive predictive value, and negative predictive value of the HHV-6 LAMP method without DNA extraction were 95.5%, 95.2%, 94.0%, and 96.4%, respectively. CONCLUSION: Direct detection of HHV-6 DNA in serum with a modified HHV-6 LAMP could be used for rapid diagnosis of exanthem subitum (ES).

Investigation of a Rotavirus Gastroenteritis Outbreak among Immunosuppressed Patients in a Hospital Setting.

Objective: Rotavirus (RV) is the most common cause of severe dehydrating diarrhoea in healthy infants and young children. The aims of this study were to investigate a RV outbreak in the pediatric hematology and oncology ward and to examine possible associations between immune status and RV infection. Patients and methods: Twenty-eight children (19 boys and 9 girls) who were hospitalized for treatment of hematological malignancy and solid organ tumor during the RV outbreak were enrolled in this study. Fourteen of the 28 patients developed RV gastroenteritis (GE) during the observation period. RV antigen and RV IgG and IgA were measured by enzyme-linked immunosorbent assays. RV G and P types were determined by reverse transcriptase-polymerase chain reaction. Results: Mean duration of RVGE in 14 patients was 13.9 days and mean severity score was 7.4. Two RV strains (G3P [8] and G2P [4]) were mainly circulating in the ward, which might result in the formation of a reassortant G2P [8] strain and mixed infection with G2+3P [8] in the immunocompromised patients. RV antigenemia was detected in 22 of the 28 patients (78.6%). RV-specific IgG titers in acute-phase sera of RVGE group were significantly lower than those in non-RVGE group (P=0.001). Mean age of the patients was significantly lower in RVGE group (5.5 ± 4.6 years) than non RVGE group (10.6 ± 4.5 years) (P=0.015). Conclusion: Our data demonstrate that host factors including age, underlying diseases, and immune status may be associated with the susceptibility of RV infection in immunocompromised patients at the time of the nosocomial infection.

Evaluating the effectiveness of the universal immunization program against varicella in Japanese children.

OBJECTIVE: Matched case control study was conducted to elucidate the effectiveness of the Oka/Biken vaccine immediately after implementation of the universal immunization program in Japan. METHODS: Cases were laboratory confirmed varicella patient under 15years of age diagnosed at 14 designated pediatric clinics between September 2015 and September 2016. Controls were selected from patients who visited the same practice for different reasons as the varicella case within 2weeks. Swab samples were collected from varicella suspected patients and molecular diagnostic assays were used to confirm varicella cases. Matched odds ratio were used to calculate vaccine effectiveness (VE). RESULTS: Varicella zoster virus DNA was detected in 183 (81.3%) of 225 suspected cases. One sample was excluded because it was positive for the Oka vaccine strain (182/225, 80.9%). Three hundred twenty-three control subjects were enrolled. The effectiveness of 1 dose of the Oka/Biken vaccine compared with no vaccine was 76.7% (95% confidence interval [CI]: 58.6-86.9%; P<0.001). The effectiveness of 2 doses of the Oka/Biken vaccine was 94.2% (95% CI: 85.7-97.6%; P<0.001). After adjusting for potential confounding effects, the adjusted VE of 1 and 2 doses of varicella vaccine were 76.9% (95% CI: 58.1-87.3%; P<0.001) and 94.7% (95% CI: 86.0-98.0%; P<0.001), respectively. CONCLUSIONS: VE of one dose of Oka/Biken varicella vaccine was insufficient to control varicella. Therefore, two doses of Oka/Biken varicella vaccine is significant for controlling varicella in Japan.